Processing device, network device, control method of processing device, control method of network device, and recording medium

ABSTRACT

A processing device according to one aspect of the present invention includes a provider configured to provide a process to a first device connected to a network of a process control system in a plant, an acquirer configured to acquire a live list generated by the first device based on diagnostic communication packets transmitted from the first device at predetermined time intervals, the live list comprising information indicating whether communication between the first device and another processing device that provides a process to the first device is norma, the processing device and the another processing device constituting a redundant pair 1, and a switch configured to switch a state of the provider from a standby state in which the provider is on standby to provide the process to the first device to an active state in which the provider provides the process to the first device based on the acquired live list.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a processing device, a network device,a control method of a processing device, a control method of a networkdevice, and a recording medium.

The present application claims priority based on Japanese patentapplication 2016-187491, filed on Sep. 26, 2016 and includes herein byreference the content thereof.

Description of Related Art

In the related art, a distributed control system (DCS) in which fielddevices such as measurement devices or operation devices called fielddevices and a control device that controls the field devices areconnected through communication means is established in a factory or aplant (hereinafter, referred to as a “plant” in a case where the plantand the factory are commonly termed) such as an industrial plantincluding a chemical plant, a plant that manages and controls a wellsite such as a gas field or an oil field or the periphery thereof, aplant that manages and controls generation of hydraulic power, thermalpower, or nuclear power, a plant that manages and controls environmentalpower generation such as solar power and wind power, or a plant thatmanages and controls a water supply and sewage system or a dam. In sucha DCS, an advanced automatic operation is realized.

There are some cases where high reliability and real-time properties arerequired in a plant system established for realizing an advancedautomatic operation described above. For example, feedback control inwhich a processing result is fed back as an input of the processing andthe feedback result is used is often used in control of the plant suchas process control. In the feedback control, if a loss occurs inprocessing data, stability of the control is lowered.

Thus, in the control of the plant, there are some cases where aredundant system which has a redundant configuration using a pluralityof devices is used in order to improve availability of the system. Forexample, the redundant system includes a processing device ordinarilyused and another processing device used when it is determined that theprocessing device is abnormal based on a heartbeat signal (to bedescribed below) from the processing device. The abnormally usedprocessing device is in a standby state and does not perform a controlprocess when the ordinarily used processing device is operated. Theordinarily used processing device outputs the heartbeat signal fornotifying that a resource of the processing device is normally operatedat predetermined time intervals. The abnormally used processing devicemonitors the heartbeat signal of the ordinarily used processing device,is switched from the standby state to an active state when theabnormality of the heartbeat signal is detected, and performs thecontrol process instead of the abnormal resource of the ordinarily usedprocessing device (for example, see Japanese Unexamined PatentApplication, First Publication No. 2000-218476 or PCT InternationalPublication No. WO2015-098589).

In a control network used in the control of the plant, in order todetermine that a communication path between devices connected to thecontrol network is normal, each of the devices broadcasts a diagnosticcommunication packet which is a packet for diagnosing communication in afixed cycle. The diagnostic communication packet includes identificationinformation of a transmission source. The device that receives thediagnostic communication packet generates or updates a live listacquired listing the devices which are the transmission sources, andretains information items of the devices capable of communicating (forexample, see Japanese Unexamined Patent Application, First PublicationNo. 2015-092400).

In the system of the related art, it is necessary to add a function(hardware or software) of performing a dedicated process such as ageneration process or a reception process of the heartbeat signal inorder to establish the redundant system, and device cost may be raised.

For example, even though a resource that provides a process is normal,in a case where the added function is abnormal like in a case wherewiring through which the heartbeat signal is transmitted and received isdisconnected, the abnormally used processing device detects abnormalityof the heartbeat signal, and is switched from the standby state to theactive state. Thus, a so-called split-brain syndrome (hereinafter,abbreviated as “SB”) in which data inconsistency due to duplication ofthe process occurs may occur, and the process may be unstable.

The live list is acquired by listing the devices of which communicationstates are normal, and is not for use in the redundant system.

One aspect of the present invention provides a processing device, anetwork device, a control method of a processing device, a controlmethod of a network device, and a recording medium which are capable ofrealizing a high-stability redundant configuration with low cost.

SUMMARY

A processing device according to one aspect of the present invention mayinclude a provider configured to provide a process to a first deviceconnected to a network of a process control system in a plant, anacquirer configured to acquire a live list generated by the first devicebased on diagnostic communication packets transmitted from the firstdevice at predetermined time intervals, the live list comprisinginformation indicating whether communication between the first deviceand another processing device that provides a process to the firstdevice is normal, the processing device and the another processingdevice constituting a redundant pair, and a switch configured to switcha state of the provider from a standby state in which the provider is onstandby to provide the process to the first device to an active state inwhich the provider provides the process to the first device based on theacquired live list.

In the above-described processing device, the acquirer may be configuredto acquire a plurality of live lists. The switch may be configured toswitch the state of the provider from the standby state to the activestate when all the plurality of live lists acquired within apredetermined period include the information indicating that thecommunication between the first device and the another processing deviceis not normal.

The above-described processing device may further include a receiverconfigured to receive the diagnostic communication packets, a generatorconfigured to generate the live list based on the received diagnosticcommunication packets, and a transmitter configured to transmit thegenerated live list as a part of diagnostic communication packets of theprocessing device at predetermined time intervals.

In the above-described processing device, the transmitter may beconfigured to transmit the diagnostic communication packets to allcommunication destinations that communicate when the process of theprocessing device is used in the first device.

In the above-described processing device, the generator may beconfigured to generate the live list based on the diagnosticcommunication packets of all communication destinations that communicatewhen the other processing device is used.

A processing device according to another aspect of the present inventionmay include a provider configured to provide a process to a first deviceconnected to a network of a process control system in a plant, atransmitter configured to transmit diagnostic communication packets atpredetermined time intervals, and an acquirer configured to acquire alive list based on diagnostic communication packets generated by thefirst device and transmitted from the first device at predetermined timeintervals, the live list comprising information on operation state ofdevices of transmission sources of the diagnostic communication packets.

In the above-described processing device, the transmitter may beconfigured to transmit the diagnostic communication packets to allcommunication destinations that communicate when the process of theprocessing device is used in the first device.

The above-described processing device may further include a switchconfigured to switch a state of the provider to a standby state in whichthe provider is on standby to provide the process to the first devicebased on the acquired live list.

In the above-described processing device, the switch may be configuredto analyze a communication state of a communication path between theprocessing device and the first device using the live list acquiredwithin a predetermined period, and switch the state of the provider tothe standby state when a communication state between the first deviceand another processing device that provides a process to the firstdevice has a priority higher than a communication state between thefirst device and the processing device. The transmitter may beconfigured to stop the transmitting of the diagnostic communicationpackets.

The above-described processing device may further include a receiverconfigured to receive diagnostic communication packets transmitted fromanother processing device that provides a process to the first device,and a generator configured to generate a live list based on the receiveddiagnostic communication packets. The transmitter may be configured totransmit the generated live list as a part of the diagnosticcommunication packets of the processing device at predetermined timeintervals.

A network device connected to a network of a process control system in aplant according to still another aspect of the present invention mayinclude a receiver configured to receive diagnostic communicationpackets transmitted from a processing device that provides a process toa first devices connected to the network at predetermined timeintervals, a generator configured to generate a live list based on thereceived diagnostic communication packets, the live list comprisinginformation on operation state of devices of transmission sources of thediagnostic communication packets, and a transmitter configured totransmit the generated live list as a part of diagnostic communicationpackets of the network device at predetermined time intervals.

A control method of a processing device according to still anotheraspect of the present invention may include providing a process to afirst device connected to a network of a process control system in aplant, acquiring a live list generated by the first device based ondiagnostic communication packets transmitted from the first device atpredetermined time intervals, the live list comprising informationindicating whether communication between the first device and anotherprocessing device that provides a process to the first device is normal,the processing device and the another processing device constituting aredundant pair, and switching a provision state of the process from astandby state in which the processing device is on standby to providethe process to the first device to an active state in which theprocessing device provides the process to the first device based on theacquired live list.

A control method of a processing device according to still anotheraspect of the present invention may include providing a process to afirst device connected to a network of a process control system in aplant, transmitting diagnostic communication packets at predeterminedtime intervals, and acquiring a live list based on diagnosticcommunication packets generated by the first device and transmitted fromthe first device at predetermined time intervals, the live listcomprising information on operation state of devices of transmissionsources of the diagnostic communication packets.

A control method of a network device connected to a network of a processcontrol system in a plant according to still another aspect of thepresent invention may include receiving diagnostic communication packetstransmitted from a processing device that provides a process to a firstdevice connected to the network at predetermined time intervals,generating a live list based on the received diagnostic communicationpackets, the live list comprising information on operation state ofdevices of transmission sources of the diagnostic communication packets,and transmitting the generated live list as a part of diagnosticcommunication packets of the network device at predetermined timeintervals.

A non-transitory computer-readable storage medium storing a controlprogram of a processing device according to still another aspect of thepresent invention, which when executed by a computer, may cause thecomputer to execute providing a process to a first device connected to anetwork of a process control system in a plant, acquiring a live listgenerated by the first device based on diagnostic communication packetstransmitted from the first device at predetermined time intervals, thelive list comprising information indicating whether communicationbetween the first device and another processing device that provides aprocess to the first device is normal, the processing device and theanother processing device constituting a redundant pair, and switching aprovision state of the process from a standby state in which theprocessing device is on standby to provide the process to the firstdevice to an active state in which the processing device provides theprocess to the first device based on the acquired live list.

A non-transitory computer-readable storage medium storing a controlprogram of a processing device according to still another aspect of thepresent invention, which when executed by a computer, may cause thecomputer to execute providing a process to a first device connected to anetwork of a process control system in a plant, transmitting diagnosticcommunication packets at predetermined time intervals, and acquiring alive list based on diagnostic communication packets generated by thefirst device and transmitted from the first device at predetermined timeintervals, the live list comprising information on operation state ofdevices of transmission sources of the diagnostic communication packets.

A non-transitory computer-readable storage medium storing a controlprogram of a network device which is connected to a network of a processcontrol system in a plant according to still another aspect of thepresent invention, which when executed by a computer, may cause thecomputer to execute receiving diagnostic communication packetstransmitted from a processing device that provides a process to a firstdevice connected to the network at predetermined time intervals,generating a live list based on the received diagnostic communicationpackets, the live list comprising information on operation state ofdevices of transmission sources of the diagnostic communication packets,and transmitting the generated live list as a part of diagnosticcommunication packets of the network device at predetermined timeintervals.

According to one aspect of the present invention, it is possible toprovide a processing device, a network device, a control method of aprocessing device, a control method of a network device, and a recordingmedium which are capable of realizing a high-stability redundantconfiguration with low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration example of a processingsystem according to an embodiment.

FIG. 2 is a diagram showing an example of a diagnostic communicationpacket according to the embodiment.

FIG. 3 is a diagram showing an example of a live list according to theembodiment.

FIG. 4 is a flowchart showing an example of a transmission operation ofthe diagnostic communication packet according to the embodiment.

FIG. 5 is a flowchart showing an example of an updating operation of thelive list according to the embodiment.

FIG. 6 is a flowchart showing an example of a switching operation of aprocessing device according to the embodiment.

FIG. 7 is a diagram showing an example of the updating of the live listaccording to the embodiment.

FIG. 8 is a diagram showing an example of a searched result of the livelist according to the embodiment.

FIG. 9 is a diagram showing a second configuration example of theprocessing device according to the embodiment.

FIG. 10 is a diagram showing an example of an app communication path ofa processing system according to the embodiment.

FIGS. 11A and 11B are diagrams showing examples of logical coupling oflive lists according to the embodiment.

FIG. 12 is a flowchart showing an example of the switching operation ofthe processing device according to the embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a processing device, a network device, a control method ofthe processing device, a control method of the network device, and arecording medium according to an embodiment of the present inventionwill be described in detail with reference to the drawings.

Initially, a configuration of a processing system will be described withreference to FIG. 1. FIG. 1 is a diagram showing a configuration exampleof a processing system according to the embodiment.

In FIG. 1, a processing system 10 includes a processing device 11, aprocessing device 12, a terminal device 13, and a terminal device 14.Initially, the outlines of the processing device 11, the processingdevice 12, the terminal device 13, and the terminal device 14(hereinafter, may be referred to as “the processing device and thelike”) will be described. The processing device and the like may bedevices constituting a process control system in a plant connected via anetwork. The processing device and the like may include network devicessuch as a gateway device (not shown). For example, the processing deviceand the like are general-purpose computers such as a server device, adesktop PC, a laptop PC, a tablet PC, a PDA, and a smartphone. Theprocessing device and the like may be dedicated devices constituting theprocess control system in the plant, such as a maintenance informationmanagement server that manages maintenance information in the plant, aDCS control device, a factory automation (FA) computer, a programmablelogic controller (PLC), an operation-monitoring device, and an operatorconsole. The processing device and the like may be field devices or amaintenance-dedicated device that carries out maintenance of the fielddevices. For example, the field device may be an input device thatinputs a signal of a physical quantity (pressure or temperature) of adifferential pressure gauge, a thermometer, or a flowmeter or an outputdevice that outputs a control signal for changing an opening degree of aregulating valve. For example, the maintenance-dedicated device is adevice that performs maintenance items such as a loop test, zero pointadjustment, and span adjustment on the field device.

It is assumed that the processing device and the like include a centralprocessing unit (CPU), a random-access memory (RAM), a read-only memory(ROM), a hard disk drive (HDD), a display device, and an input devicesuch as a keyboard or a mouse, which are not shown. As for the functionsof the processing device 11, the processing device 12, the terminaldevice 13, and the terminal device 14 which are described below, thefunction of each device may be realized by causing the CPU to execute aprogram stored in the RAM. That is, the function of the processingdevice is a functional module to be realized by software. The program tobe executed by the processing device may be provided from a server thatprovides the program, or may be provided from a recording medium.

The processing device 11 is a device (active-side device) that providesa predetermined process to the terminal device 13 and the terminaldevice 14 connected via a network 19. The processing device 11 is pairedwith the processing device 12 (standby-side device), and constitutes aredundant system. For example, the process provided by the processingdevice 11 is a typical process control process performed by a controllerconstituting the process control system in the plant, and is a serviceprovided by the processing device monitored using a live list to bedescribed below in the present embodiment. The process provided by theprocessing device may be a generic server process, and may be adaemon-related service or a virtual IP service. The service provided bythe processing device to be monitored is provided by an operationenvironment (platform) of hardware or a hypervisor (virtualization) thatexecutes an OS 112 and an app (short for application; the same applieslater) 113. Accordingly, the processing device may be monitored bymonitoring whether or not the operation environment (platform) isoperated. The service provided by the processing device to be monitoredmay be the OS or the app itself. For example, the service may be aprocess such as data processing, data storing, data transmission, acommunication service, or a web service on a web browser which isprovided via the network. The service provided by the processing devicemay be monitored for each process. The device that uses the processprovided by the processing device 11 in the present embodiment isreferred to as a utilization device. The terminal device 13 and theterminal device 14 are examples of the utilization device.

The processing device 11 broadcasts a diagnostic communication packet(SP11) via the network 19. The diagnostic communication packet is anexample of a diagnostic communication packet indicating that theprocessing device is normally operated. The device which receives thediagnostic communication packet and is connected to the network 19 maydiagnose that an operation state of the device (processing device 11)which is a transmission source of the received diagnostic communicationpacket and a communication state of a communication path between theprocessing device and the device as the transmission source are normal.For example, the device that receives the diagnostic communicationpacket may perform a process for selecting the device which is thetransmission source of the diagnostic communication packet, as acommunication destination. FIG. 1 shows that the diagnosticcommunication packet (SP11) is transmitted to only the terminal device13 and the terminal device 14.

It is assumed in the present embodiment that the processing device 12,the terminal device 13, and the terminal device 14 broadcast thediagnostic communication packets (SP12 to SP14) via the network 19. Thatis, an example in which each of these devices respectively transmits thediagnostic communication packet indicating that each of the devices isnormally operated to the device connected to the network 19 isillustrated.

It is assumed that each of the processing device 11, the processingdevice 12, the terminal device 13, and the terminal device 14 generatesa live list based on the received diagnostic communication packet andbroadcasts the generated live list as data of the diagnosticcommunication packet to be transmitted from each of these devices. Thegeneration and transmission of the live list will be described indetail.

The processing device 12 is paired with the processing device 11, andthese devices constitute the redundant system (redundant deviceconfiguration). The processing device 12 performs the process providedby the processing device 11 instead of the processing device 11 when theprocessing device 11 becomes abnormal. This process indicates a processto be performed by the OS and the app which only operate on theprocessing device in an active state. The processing device 12 does notprovide the process in a standby state when the processing device 11 isnormally operated. The processing device 12 substitutes for theprocessing device 11 by starting to provide the process after changingfrom the standby state to the active state when the processing device 11becomes abnormal. The processing device in the standby state may bereferred to as a “standby-side device” or the device in the active statemay be referred to as an “active-side device”. The processing device 12broadcasts the diagnostic communication packet (SP12) (not shown)through the network 19.

The terminal device 13 and the terminal device 14 are devices which areconnected to the network 19 except for the processing device 11 or theprocessing device 12 among the network devices constituting the processcontrol system in the plant, and are examples of the communicationdestinations of the processing device 11 or the processing device 12.The terminal device 13 and the terminal device 14 in FIG. 1 are theutilization devices that use the process provided by the processingdevice 11 or the processing device 12, and are examples of theprocessing device of a single configuration that does not constitute theredundant configuration. The terminal device 13 and the terminal device14 broadcast the diagnostic communication packets (SP13 and SP14) viathe network 19 (partially not shown).

Hereinafter, an internal configuration of each of the processing device11, the processing device 12, the terminal device 13, and the terminaldevice 14 will be described.

The processing device 11 has functions of a network interface card (NIC)111, an OS 112, an app 113, a diagnostic communication receiver 114, alive list generator 115, a diagnostic communication data generator 116,and a diagnostic communication transmitter 117.

The NIC 111 is an example of a communication function of performingcommunication via the network 19. The NIC 111 includes an appcommunication address which is an example of first identificationinformation and a diagnostic communication address which is an exampleof second identification information.

The app communication address is identification information forcommunicating with the app 113 operated on the OS 112, and is anidentifier for uniquely determining the app 113 which is a communicationpartner within the network. The app communication address in a casewhere these devices constitute the redundant configuration is set to theactive-side device in which the app is operated, and is not set to thestandby-side device in which the app is not operated. In a case wherethe active-side device is switched from the PC11 to the PC12, the appcommunication address is set (transitions) to only the PC 12 which isthe active-side device. For example, an Internet Protocol (IP) addressor an application-dedicated identifier may be used as the appcommunication address. For example, the application-dedicated identifiermay be a device address of a control bus for process control thatenables communication between the devices connected to the network suchas Vnet (registered trademark).

The diagnostic communication address of the processing device 11 is anidentifier for uniquely determining an individual device connected tothe network. Even though the device in the active state is switched in acase where these devices constitute the redundant system, the diagnosticcommunication address is fixed. An IP address or a MAC address that usesan address closer to a physical layer than the app communication addressmay be used as the diagnostic communication address. For example, thediagnostic communication address of the processing device 11 is added asinformation for identifying the transmission source to the diagnosticcommunication packet, and thus, the terminal device 13 that receives thediagnostic communication packet may determine that packet transmissionto the terminal device 13 from the processing device 11 is normal in thetransmission and reception of the packet to and from the processingdevice 11.

In the present embodiment, the app communication address which is anexample of the first identification information and the diagnosticcommunication address which is an example of the second identificationinformation use the same NIC 111. Accordingly, for example, in a casewhere a load of communication using the app communication address ishigh, the transmission and reception of the diagnostic communicationpacket using the diagnostic communication address may fail. For example,a priority in the transmission and reception of the diagnosticcommunication packet becomes higher than a priority in the appcommunication using a priority service defined in IEEE 802.1p, and thus,it is possible to reduce a possibility that the communication of thediagnostic communication packet will fail even in a case where a load ofthe app communication is high.

The first identification information such as an app communicationaddress which is the identifier specific to the app and the secondidentification information such as an IP address are allocated to thesame NIC 111, and thus, the first identification information and thesecond identification information may have the same degree ofavailability to the network 19. For example, the first identificationinformation and the second identification information may not besimilarly used (operated) for cable detachment or disconnection of a LANcable connected to the NIC 111 or a communication failure related to theNIC 111 such as a failure of the NIC 111. Accordingly, when thetransmission of the diagnostic communication packet using the secondidentification information cannot be performed due to the communicationfailure related to the NIC 111, the application communication using thefirst identification information cannot be performed. Accordingly, whenthe diagnostic communication packet cannot be detected due to thecommunication failure, it is possible to prevent the occurrence of SBdue to the fact that a plurality of active-side applications to whichthe same first identification information is allocated can communicate.

As stated above, the first identification information is common to thedevices, as the app communication address provided by the processingdevice 12. The terminal device 13 and the terminal device 14 can use theprocess provided by the processing device 11 and the process provided bythe processing device 12 in the redundant configuration of theprocessing system 10 without distinguishing these processes using thecommon first identification information, and thus, it is possible toimprove the degrees of availability of the terminal device 13 and theterminal device 14.

The app 113 operated on the OS 112 performs the process of the serviceprovided to the terminal device 13 through the NIC 111. The app 113 canrecognize an operation state of the device which is the partner thatprovides the service based on the live list to be described below. Inthe present embodiment, the terminal device 13 and the terminal device14 which are the utilization devices determine whether or not the OS 112and the app 113 can provide the services depending on whether or not thediagnostic communication packet can be received.

The diagnostic communication receiver 114 receives the diagnosticcommunication packet transmitted from another device connected to thenetwork 19. In FIG. 1, the diagnostic communication receiver 114receives the diagnostic communication packets transmitted from theprocessing device 12, the terminal device 13, and the terminal device14. Since timings when the diagnostic communication packets aretransmitted are determined in the devices on the transmitter side,reception timings of the diagnostic communication packets received bythe diagnostic communication receiver 114 from the processing device 12,the terminal device 13, and the terminal device 14 are not synchronized.The diagnostic communication receiver 114 transmits the receiveddiagnostic communication packets to the live list generator 115. Thediagnostic communication receiver 114 transmits the diagnosticcommunication packet to the live list generator 115 whenever thediagnostic communication packet is received. Here, the diagnosticcommunication receiver 114 may transmit the diagnostic communicationpackets received within a predetermined time to the live list generator115 at one time.

The live list generator 115 receives the diagnostic communicationpackets from the diagnostic communication receiver 114, and generatesthe live list. The live list is a list (live information) acquired bylisting information items of the operation states of the devices whichare the transmission sources of the received diagnostic communicationpackets and information items of communication states of communicationpaths between the devices which are the transmission sources and theprocessing device itself. These information items are updated based onwhether the diagnostic communication packets are received or not withina predetermined time. When the diagnostic communication packets arereceived within the predetermined time, the operation states of thedevices which are the transmission sources and the communication statesof the communication paths are set to “operation/being operated”. Whenthe diagnostic communication packets are not received within thepredetermined time, the operation states of the devices which are thetransmission sources and the communication states of the communicationpaths are set to “stoppage/being stopped”. Since the devices connectedto the network 19 respectively transmit the diagnostic communicationpackets, the transmission and reception of the diagnostic communicationpackets are mutually performed between two devices. Since the live listgenerator 115 lists the devices of which the diagnostic communicationpackets are received, the live list generated in the live list generator115 is acquired by listing the devices of which communication is normalin the transmission of the diagnostic communication packets from otherdevices to at least the processing device 11.

The diagnostic communication packets are transmitted so as to cover allused app communication paths. The app communication paths arecommunication paths used by the apps on the processing device and theutilization device in the network 19, and include communication pathsrelayed by the network devices such as a gateway device (not shown). Ina case where the app communication paths are relayed by the gatewaydevice, the gateway is also the transmission target of the diagnosticcommunication packet. The live list generator 115 generates the livelist based on the diagnostic communication packets of all thecommunication destinations which communicate in the app communicationpaths. Accordingly, in a case where the app communication paths arerelayed by the gateway device, the gateway device is also included inthe generated live list. Accordingly, if any one of the appcommunication paths is normal, the diagnostic communication packets ofthe active-side devices are received. In a case where all the diagnosticcommunication packets of the active-side devices are not received, allthe app communication paths are abnormal or the processing device itselffails, and thus, the diagnostic communication packets are nottransmitted. The live list is used, and thus, it is possible to preventthe occurrence of the SB even in a case where the processing device inthe standby state enters the active state.

The live list generator 115 stores the generated live list such that thelive list can be read from the app 113 and the diagnostic communicationdata generator 116. For example, the live list may be stored in a RAM oran HDD (all not shown). The app 113 and the diagnostic communicationdata generator 116 may read the stored live list in an arbitrary timing.

The diagnostic communication data generator 116 generates the diagnosticcommunication packet. The diagnostic communication data generator 116adds information for identifying the processing device 11 to thediagnostic communication packet. An IP address or a MAC address fordiagnostic communication of the processing device 11 may be used as theinformation for identifying the processing device 11. The diagnosticcommunication data generator 116 adds the live list generated in thelive list generator 115 to an IP data portion of the generateddiagnostic communication packet.

The diagnostic communication transmitter 117 transmits the diagnosticcommunication packets generated in the diagnostic communication datagenerator 116 so as to cover all the used app communication paths asdescribed above. The diagnostic communication transmitter 117 broadcaststhe diagnostic communication packets to the network 19 through the NIC111 in a predetermined timing. For example, the timing when thediagnostic communication transmitter 117 transmits the diagnosticcommunication packet is a predetermined time interval (transmissioncycle). The diagnostic communication transmitter 117 may instruct thediagnostic communication data generator 116 to generate the diagnosticcommunication packets when the time reaches the transmission cycle, andmay acquire and broadcast the diagnostic communication packets generatedin the diagnostic communication data generator 116. Although it has beendescribed in the present embodiment that the diagnostic communicationtransmitter 117 broadcasts the diagnostic communication packet, in acase where the device that receives the diagnostic communication packetis limited, multicast or unicast may be used instead of the broadcast.The diagnostic communication transmitter 117 may perform broadcasttransmission of the diagnostic communication packet to a network ofanother segment that crosses a router (may transmit the diagnosticcommunication packet to a directed broadcast address).

The processing device 12 has functions of a NIC 121, an OS 122, an app123, a diagnostic communication receiver 124, a live list generator 125,a diagnostic communication data generator 126, a diagnosticcommunication transmitter 127, a live list analyzer 128, a devicestoppage detector 129, and a switch 120.

A configuration of the NIC 121 is the same as the configuration of theNIC 111. That is, similarly to the NIC 111, the NIC 121 is an example ofa communication function of performing communication via the network 19.The NIC 121 also has the app communication address which is an exampleof the first identification information and the diagnostic communicationaddress which is the example of the second identification information.The app communication address of the NIC 121 is the same as the appcommunication address of the NIC 111.

The OS 122 and the app 123 are switched between the standby state andthe active state. When the app 123 enters the active state, the processcommon to the processing device 11 is provided using the appcommunication address which is the first identification information ofthe NIC 121. Meanwhile, the process is not provided when the app 123enters the standby state. Dashed lines of the OS 122 and the app 123shown in FIG. 1 represent that the OS 122 and the app 123 are in thestandby state.

The OS 122 and the app 123 are switched (transitions) from the standbystate to the active state based on a request from the switch 120. The OS122 and the app 123 transition to the active state, and thus, the app123 continues the process instead of the app 113. The transition fromthe active state to the standby state may be performed based on aresuming of the processing device 12.

The functions of the diagnostic communication receiver 124, the livelist generator 125, the diagnostic communication data generator 126, andthe diagnostic communication transmitter 127 are the same as thefunctions of the diagnostic communication receiver 114, the live listgenerator 115, the diagnostic communication data generator 116, and thediagnostic communication transmitter 117 in the processing device 11,and thus, the description thereof will be omitted. Here, the diagnosticcommunication receiver 124 transmits the received diagnosticcommunication packet to the live list generator 125, and also transmitsthe received diagnostic communication packet to the live list analyzer128.

The live list analyzer 128 acquires the live list included in thediagnostic communication packet from the diagnostic communicationreceiver 124, searches the processing device 11 which is the pairedprocessing device constituting the redundant system from the acquiredlive list, and updates and records the state of the processing device11. It is assumed that the state of the processing device 11 is referredto as active-side device live information. The diagnostic communicationpackets are acquired from the processing device 11, the terminal device13, and the terminal device 14 in the processing device 12, but it isassumed that the live list analyzer 128 uses the diagnosticcommunication packets acquired from the terminal device 13 and theterminal device 14 that use the process provided by the processingdevice 11, as search targets. That is, the live list analyzer 128acquires and records the state of the processing device 11 when viewedfrom the utilization device that uses the process provided by theprocessing device 11. The live list analyzer 128 updates the state ofthe processing device 11 of the active-side device live informationbased on the live list included in the diagnostic communication packetacquired from the terminal device 13 and the live list included in thediagnostic communication packet acquired from the terminal device 14.

The live lists acquired by the diagnostic communication receiver 124 areindividually acquired from the terminal device 13 and the terminaldevice 14 in an asynchronous manner. Accordingly, the live list analyzer128 updates the state of the processing device 11 at a timing when eachdiagnostic communication packet is acquired. As mentioned above, sincethe active-side device live information items are individually updatedbased on the live list of the terminal device 13 and the live list ofthe terminal device 14, there is no problem about a writing timing inthe updating of the state of the processing device 11. In a case wherethe diagnostic communication packet is not received within apredetermined time, the live list analyzer 128 does not refer to thelive list of the terminal of which the diagnostic communication packetis not received. Accordingly, the live list analyzer 128 regards thelive list of the terminal of which the diagnostic communication packetis not received within a predetermined time as being in the “stoppage”state, and updates the state of the processing device 11 of theactive-side device live information to be in the “stoppage” state. Forexample, the active-side live device live information is recorded in aRAM (not shown) so as to be read from the device stoppage detector 129.

The device stoppage detector 129 determines that the processing device11 is being stopped in a case where all the recorded active-side devicelive information items indicate the “stoppage” state, and instructs theswitch 120 to switch the state of the app 123 to be active. In a casewhere the “stoppage” state of the processing device 11 is recorded inthe live list or in a case where the live list is not updated within apredetermined time, the active-side device live information indicatesthat the state of the processing device 11 of the terminal device (theterminal device 13 or the terminal device 14) is “stopped”. The devicestoppage detector 129 determines that the processing device 11 is beingstopped in a case where both the state of the processing device 11 basedon the live list of the terminal device 13 and the state of theprocessing device 11 based on the live list of the terminal device 14are “stopped”. Meanwhile, the device stoppage detector 129 determinesthat the processing device 11 is being operated in a case where any oneof the state of the processing device 11 based on the live list of theterminal device 13 and the state of the processing device 11 based onthe live list of the terminal device 14 is in the “operation” state. Ina case where the processing device 11 is actually stopped, since thestates of the processing devices 11 of all the live lists enter the“stoppage” state, in a case where any one of the live lists is in the“operation” state, it may be possible to determine that the processingdevice 11 is being operated. Accordingly, the device stoppage detector129 can perform determination for distinguishing between a case wherethe processing device 11 is actually stopped and a case where a failureoccurs in a part of packet communication due to the network failure eventhough the processing device 11 is being actually operated.

The switch 120 performs a process for requesting that the app 123 is toswitch from the standby state to the active state according to aninstruction from the device stoppage detector 129. A redundant operationis a state in which two devices are prepared such that the standby-sidedevice is switched to the active-side device in a redundant deviceconfiguration in which two general-purpose devices are connected via anetwork. For example, in the case of fault tolerance, if a memory or adisk of the active-side device is changed, a changing location is copiedto the standby-side device and is equalized. The terminal device 13 hasfunctions of a NIC 131, an OS 132, an app 133, a diagnosticcommunication receiver 134, a live list generator 135, a diagnosticcommunication data generator 136, and a diagnostic communicationtransmitter 137. The terminal device 14 has functions of a NIC 141, anOS 142, an app 143, a diagnostic communication receiver 144, a live listgenerator 145, a diagnostic communication data generator 146, and adiagnostic communication transmitter 147.

The functions of the NIC 131, the OS 132, the app 133, the diagnosticcommunication receiver 134, the live list generator 135, the diagnosticcommunication data generator 136, and the diagnostic communicationtransmitter 137 of the terminal device 13 are conformable to thefunctions of the NIC 111, the OS 112, the app 113, the diagnosticcommunication receiver 114, the live list generator 115, the diagnosticcommunication data generator 116, and the diagnostic communicationtransmitter 117 of the processing device 11.

The app 133 uses any one of the process provided by the app 113 of theprocessing device 11 and the process provided by the app 123 of theprocessing device 12. The app 133 can continuously use the processprovided by the app 123 operated instead of the app 113 using the appcommunication address which is the first identification informationcommon between the processing device 11 and the processing device 12even though the process provided by the app 113 is stopped.

Although it has been described in FIG. 1 that the diagnosticcommunication packets are respectively broadcast from the devicesconnected to the network 19, in a case where the gateway device such asa router is connected to the network 19 and communication is limited,the transmission destination of the diagnostic communication packet maybe limited by the gateway device.

It has been described in FIG. 1 that the functions of the processingdevice 11, the processing device 12, the terminal device 13, and theterminal device 14 are realized by software. However, one or morefunctions of the processing device 11, the processing device 12, theterminal device 13, and the terminal device 14 may be realized byhardware. As for the functions of the processing device 11, theprocessing device 12, the terminal device 13, and the terminal device14, one function may be realized by being divided into a plurality offunctions. As for the functions of the processing device 11, theprocessing device 12, the terminal device 13, and the terminal device14, two or more functions may be realized by being aggregated into onefunction.

Hereinabove, a description of the configuration of the processing systemusing FIG. 1 has been described.

Hereinafter, the diagnostic communication packet generated in thediagnostic communication data generator 116 which is described in FIG. 1will be described with reference to FIG. 2. FIG. 2 is a diagram showingan example of the diagnostic communication packet according to theembodiment.

In FIG. 2, the diagnostic communication packet represents an IP packetincluding an IP header portion and an IP data portion. The IP headerportion of the diagnostic communication packet includes an IP addresswhich is a transmission source of a packet and an IP address which is adestination thereof. FIG. 2 shows a case where the transmission sourceis the processing device 12 and the destination is the broadcast. An IPaddress (192.168.1.2) which is the diagnostic communication address ofthe processing device 12 is illustrated as the transmission source. AnIP address (192.168.1.255) for broadcast is illustrated as thedestination address. In the present embodiment, it is not necessary toinput information related to the transmission source into the IP dataportion using the transmission source address of the diagnosticcommunication packet as the diagnostic communication address, and thus,it is possible to reduce a packet transmission and reception load.

Information of the live list generated in the live list generator 125 isinput into the IP data portion of the diagnostic communication packet.The diagnostic communication packet may indicate that communication of apacket transmitted from the transmission source is normal by includingthe identification information (for example, the IP address of thetransmission source) of the transmission source. Accordingly, in aconventional case where the diagnostic communication packet indicatesonly that the communication of the packet transmitted from thetransmission source is normal, data for reducing a packet data amount isnot input into the IP data portion of the diagnostic communicationpacket. In the present embodiment, it is not necessary to add a functionof separately transmitting the live list by adding the information ofthe live list to the IP data portion of the diagnostic communicationpacket unlike in a case where the live list is separately transmitted toanother device connected to the network 19, and thus, it is possible toreduce device cost. It is not necessary to transmit and receive adedicated packet for transmitting the live list using the diagnosticcommunication packet, and thus, it is possible to reduce a communicationload in the network.

Hereinabove, a description of the diagnostic communication packet usingFIG. 2 has been described.

Hereinafter, the live list included in the diagnostic communicationpacket described in FIG. 2 will be described with reference to FIG. 3.FIG. 3 is a diagram showing an example of the live list according to theembodiment. FIG. 3 shows the live list included in the diagnosticcommunication packet transmitted from the terminal device 13. In FIG. 3,the live list includes items of an “IP address” and a “state”.

The “IP address” is identification information of another device ofwhich the diagnostic communication packet is received. The live list ofFIG. 3 includes data items of all addresses of the network of which theIP addresses are 192.168.1.1 to 192.168.1.254. Among them, 192.168.1.1to 192.168.1.4 are IP addresses allocated to the processing device 11,the processing device 12, the terminal device 13, and the terminaldevice 14 which are examples of the PC11 to the PC14. 192.168.1.5 to192.168.1.254 are unused addresses. In FIG. 3, it is possible to fix adata length of the live list by previously preparing data items of alladdresses of the network, and thus, it is easy to analyze the devicethat receives the live list. Even in a case where the number of devicesconnected to the network is increased or decreased, it is possible touse the live list with no change.

The “state” is an item of the live list indicating that the devicespecified by the item of the “IP address” is being operated or stopped.A case where the “state” is “o” means that the device is being operated.A case where the “state” is “x” means that the device is being stopped,i.e. that the diagnostic communication packets are not received withinthe predetermined time. The live list of FIG. 3 shows that theprocessing device 11 and the processing device 12 are being operated,and the terminal device 14 is being stopped. Since the live list of FIG.3 is the live list transmitted from the terminal device 13, the livelist of the terminal device 13 is expressed by “-” indicating that thereis no data. The live list shows that there is no data for the unusedaddresses. The live list shown in FIG. 3 is included in the IP dataportion shown in FIG. 2 and is transmitted as the diagnosticcommunication packet.

Although the live list is represented as data in a tabular form for thesake of convenience in description in FIG. 3, the live list included inthe diagnostic communication packet may be represented in another dataform. For example, the live list may be comma-separated values (CSV)data.

Although it has been described in FIG. 3 that the data length of thelive list is fixed, the data length of the live list may be varied. Forexample, the live list includes the live lists of the processing device11, the processing device 12, the terminal device 13, and the terminaldevice 14 actually connected to the network and does not include thelive lists for the unused addresses, and thus, it is possible to reducethe data amount of the live list.

The live list may be encrypted data. Although it has been described thatthe live list of FIG. 3 includes only the live list indicating whetherthe state of the device is being operated or stopped, the live list mayinclude another information. For example, the live list may includeinformation items such as a communication speed, a packet loss, and asuccess rate of packet communication.

Hereinabove, a description of the live list using FIG. 3 has beendescribed.

Hereinafter, a transmission operation of the diagnostic communicationpacket will be described with reference to FIG. 4. FIG. 4 is a flowchartshowing an example of the transmission operation of the diagnosticcommunication packet according to the embodiment. Although it has beendescribed that the transmission operation of the diagnosticcommunication packet described in FIG. 4 is performed by the processingdevice 11, the same is true of the processing device 12, the terminaldevice 13, and the terminal device 14.

In FIG. 4, the processing device 11 resets a timer value, and starts atimer (step S11). The timer started in the process of step S11 is atimer for measuring a transmission cycle in the process of next stepS12.

After the process of step S11 is performed, the processing device 11determines whether or not the timer value reaches the transmission cycle(step S12). The transmission cycle is a cycle in which the diagnosticcommunication packet is broadcast. If the transmission cycle is short, atransmission interval of the diagnostic communication packet is shorter,and thus, a failure capable of being detected by the diagnosticcommunication packet is discovered fast. Meanwhile, if the transmissioncycle is long, the transmission interval of the diagnostic communicationpacket is long, and thus, it is possible to reduce the communicationload in the network due to the diagnostic communication packet. In acase where it is determined that the timer value does not reach thetransmission cycle (step S12: NO), the processing device 11 repeats theprocess of step S12.

Meanwhile, in a case where it is determined that the timer value reachesthe transmission cycle (step S12: YES), the processing device 11 readsthe live list (step S13). The live list is generated in the live listgenerator 115 described in FIG. 1, and is stored so as to be read fromthe diagnostic communication data generator 116. That is, the live listread in the process of step S13 is the latest information updated in thelive list generator 115.

After the process of step S13 is performed, the processing device 11generates the diagnostic communication packet (step S14). As describedin FIG. 2, the diagnostic communication packet is executed by inputtingthe live list read in the process of step S13 into the IP data portion.After the process of step S14 is performed, the processing device 11performs broadcast transmission of the diagnostic communication packetgenerated in the process of step S14 (step S15).

After the process of step S15 is performed, the processing device 11determines whether or not to end (stop) the process for transmitting thediagnostic communication packet (step S16). In a case where it isdetermined not to end the transmission process of the diagnosticcommunication packet (step S16: NO), the processing device 11 returns tothe process of step S11, and repeats the process of step S11 to stepS16. Meanwhile, in a case where it is determined to end the processingfor transmitting the diagnostic communication packet (step S16: YES),the processing device 11 ends the transmission operation of thediagnostic communication packet shown in the flowchart of FIG. 4. Theprocessing device 11 continues the transmission process of thediagnostic communication packet for a period during which the process isprovided, but ends the transmission process of the diagnosticcommunication packet in a case where the processing device 12consciously performs the process instead of the processing device 11. Ifthe transmission process of the diagnostic communication packet isended, since the processing device 12 determines that the processingdevice 11 is stopped or is disconnected from the network from thecontents of the live lists transmitted from the terminal device 13 andthe terminal device 14, the processing device 12 transitions from thestandby state to the active state.

Hereinabove, a description of the transmission operation of thediagnostic communication packet using FIG. 4 has been described.

Hereinafter, an updating operation of the live list using FIG. 5 will bedescribed. FIG. 5 is a flowchart showing an example of the updatingoperation of the live list according to the embodiment. The flowchartshown in FIG. 5 is performed in parallel for the devices that transmitthe diagnostic communication packets. For example, since the terminaldevice 13 receives the diagnostic communication packets transmitted fromthe processing device 11, the processing device 12, and the terminaldevice 14, the live list generated in the terminal device 13 includesthe live list of the processing device 11, the live list of theprocessing device 12, and the live list of the terminal device 14.Accordingly, the updating operation of the live list of the processingdevice 11, the updating operation of the live list of the processingdevice 12, and the updating operation of the live list of the terminaldevice 14 in the live list of the terminal device 13 are asynchronouslyperformed in parallel. In the following description, an example of theupdating operation of the live list of the processing device 11 in theterminal device 13 will be described. The updating operation and thelive list of the processing device 12 and the updating operation of thelive list of the terminal device 14 in the terminal device 13 aresimilarly performed. The updating operations of the live lists of theprocessing device 11, the processing device 12, and the terminal device14 are similarly performed.

In FIG. 5, the terminal device 13 resets a timer value, and starts atimer (step S21). The timer started in the process of step S21 is atimer for measuring a reception period of the diagnostic communicationpacket in the process of step S24.

After the process of step S21 is performed, the terminal device 13determines whether or not the diagnostic communication packet of theprocessing device 11 is received (step S22). The broadcast transmissionof the diagnostic communication packet of the processing device 11 isperformed in the transmission cycle described in FIG. 4. In a case whereit is determined that the diagnostic communication packet of theprocessing device 11 is received (step S22: YES), the terminal device 13updates the live list of the processing device 11 (step S23). In a casewhere the live list includes only the information indicating whether thedevice is being operated or stopped, the information indicating that thedevice is being operated is maintained.

Meanwhile, in a case where it is determined that the diagnosticcommunication packet of the processing device 11 is not received (stepS22: NO), the terminal device 13 determines whether or not the time ofthe timer is up (step S24). The value of the timer determined in theprocess of step S24 may be previously determined based on thetransmission cycle of the diagnostic communication packet of theprocessing device 11. For example, in a case where the transmissioncycle of the diagnostic communication packet of the processing device 11is Thb (seconds), it is assumed that the value of the time-up is Thb×n(n is an integer of 1 or more) (seconds). Since reception check is notperformed in the packet communication using the broadcast, there aresome cases where the diagnostic communication packet transmitted fromthe processing device 11 cannot reach the terminal device 13. Forexample, it is possible to gain three opportunities to receive thediagnostic communication packet by setting the value of the time-up tobe Thb×3 (seconds), and it is possible to reduce influence of atemporary packet loss. In a case where it is determined that the time ofthe timer is not up (step S24: NO), the terminal device 13 returns tothe process of step S22, and is on standby to receive the diagnosticcommunication packet.

Meanwhile, in a case where it is determined that the time of the timeris up (step S24: YES), the terminal device 13 updates the live list ofthe processing device 11 in the live list to be in the stoppage state(the item of the state of FIG. 3 is set to be “x”) (step S25). Even in acase where the live list is updated to be in the stoppage state in theprocess of step S25, in a case where the diagnostic communication packetis received again in the process of step S22, the live list is updatedto be in the operated state. The updated live list is included in the IPdata portion of the diagnostic communication packet of the terminaldevice 13 transmitted by reading the live list described in FIG. 4, andis broadcast from the terminal device 13.

After the process of step S23 or the process of step S25 is performed,the terminal device 13 determines whether or not to end the receptionprocess of the diagnostic communication packet (step S26). In a casewhere it is determined not to end the reception process of thediagnostic communication packet (step S26: NO), the terminal device 13returns to the process of step S21, and repeats the process of step S21to step S26. Meanwhile, in a case where it is determined to end thereception process of the diagnostic communication packet (step S26:YES), the terminal device 13 ends the reception operation of thediagnostic communication packet shown in the flowchart of FIG. 5.

For example, although the device that receives the diagnosticcommunication packet continues the reception process of the diagnosticcommunication packet for a period during which the device is beingconnected to the network, the reception process of the diagnosticcommunication packet is ended by an operation of an operator in a casewhere the device is disconnected from the network.

Hereinabove, a description of the updating operation of the live listusing FIG. 5 has been described.

Hereinafter, a switching operation of the processing device 12 will bedescribed with reference to FIG. 6. FIG. 6 is a flowchart showing anexample of the switching operation of the processing device 12 accordingto the embodiment.

In FIG. 6, it is determined whether or not the processing device 12 isin the standby state (step S31). For example, whether or not theprocessing device is in the standby state may be determined by the stateof the app 123 retained in the switch 120. In a case where it isdetermined that the processing device is not in the standby state (theprocessing device is in the active state) (step S31: NO), the processingdevice 12 ends the process of the switching operation shown in theflowchart of FIG. 6.

Meanwhile, in a case where it is determined that the processing deviceis in the standby state (step S31: YES), the processing device 12determines whether the live list of the paired processing device 11constituting the redundant configuration indicates that the device isbeing stopped in the live lists included in all the acquired diagnosticcommunication packets (step S32). Specifically, since the processingdevice 12 receives the diagnostic communication packets including thelive lists from the processing device 11, the terminal device 13, andthe terminal device 14, the processing device 12 searches for the livelists transmitted from the processing device 11, the terminal device 13,and the terminal device 14, and confirms the live list of the processingdevice 11.

In a case where it is determined that the live list of the processingdevice 11 indicates that the processing device 11 is being stopped inall the acquired live lists (step S32: YES), the processing device 12 isswitched from the standby state to the active state (step S33).Specifically, the switch 20 of the processing device 12 is switched fromthe standby state to the active state, and thus, the app 123 is set tobe in the operation state. Thus, the app 123 starts to perform theprocess of the app 113 instead of the app 113. The processing device 12that enters the active state once determines that the processing deviceis not constantly in the standby state in step S31. For example, thetransition of the processing device 12 that enters the active state tothe standby state again is performed in the restarting (reset process)of the device.

Meanwhile, in a case where it is determined that the live list of theprocessing device 11 indicates that the processing device 11 is notbeing stopped in all the acquired live lists (step S32: NO), theprocessing device 12 returns to the process of step S31, and repeats theprocess of step S31 to step S32.

Hereinabove, a description of the switching operation of the processingdevice 12 using FIG. 6 has been described.

Hereinafter, the updating of the live list of the terminal device 13 inthe process of step S25 of FIG. 5 will be described with reference toFIG. 7. FIG. 7 is a diagram showing an example of the updating of thelive list according to the embodiment.

In FIG. 7, the live list of the terminal device 14 is updated for aperiod during which the device is being operated or stopped. That is,the live list of the terminal device 13 is updated in a state in whichonly the live list of the terminal device 14 is updated. The updating ofthe live list is performed for the live lists of the devices, and thus,it is possible to reduce an updating load of the live list.

For example, the live list shown in FIG. 7 may be displayed on a displaydevice (not shown) of the terminal device 13, or may be printed from aprinting device.

Hereinabove, a description of the updating of the live list of theterminal device 13 using FIG. 7 has been described.

Hereinafter, a searched result of the live list performed by the livelist analyzer 128 of the processing device 12 will be described withreference to FIG. 8. FIG. 8 is a diagram showing an example of thesearched result of the live list according to the embodiment.

In FIG. 8, the live list analyzer 128 searches for the live list of thepaired processing device 11 constituting the redundant configurationfrom the live list of the terminal device 13 and the live list of theterminal device 14, and lists the searched results. (192.168.1.3) of theitem of the illustrated IP address indicates that the live list isacquired from the live list of the terminal device 13, and the live listindicates that the device is being operated as represented in the itemof the state. (192.168.1.4) of the item of the IP address indicates thatlive list is acquired from the live list of the terminal device 14, andthe live list indicates that the device is being operated as representedin the item of the state. The searched results shown in FIG. 8 arelisted, and thus, it is easy to determine whether or not the live listof the processing device 11 serving as the paired device indicates thatthe processing device is being stopped in the live lists included in allthe acquired diagnostic communication packets in the process of step S32of FIG. 6. For example, the searched results may be displayed on adisplay device (not shown) of the processing device 12, or may beprinted from a printing device.

Hereinabove, a description of the searched result of the live list usingFIG. 8 has been described.

Hereinafter, a second configuration example of the processing devicewill be described with reference to FIG. 9. FIG. 9 is a diagram showingthe second configuration example of the processing device according tothe embodiment.

In FIG. 9, a processing device 11 a has functions of the NIC 111, the OS112, the app 113, the diagnostic communication receiver 114, the livelist generator 115, the diagnostic communication data generator 116, thediagnostic communication transmitter 117, a live list extractor 118, alive list comparator and determiner 119, and a switch 110. The functionsof the NIC 111, the OS 112, the app 113, the diagnostic communicationreceiver 114, the live list generator 115, the diagnostic communicationdata generator 116, and the diagnostic communication transmitter 117 inthe processing device 11 a are the same as the functions of those in theprocessing device 11, and thus, the description thereof will be omitted.

The live list extractor 118 acquires the live list included in thediagnostic communication packet received by the diagnostic communicationreceiver 114, and extracts a communication state of an app communicationpath from the acquired live list. The communication path between the appand the utilization device may be divided into a communication pathrelated to transmission from the app to the utilization device and acommunication path related to transmission from the utilization deviceto the app. The live list extractor 118 extracts the communicationstates of the app communication paths in transmission directions fromthe received diagnostic communication packets.

The live list comparator and determiner 119 has a live list comparisonfunction and a live list determination function. The live listcomparison function logically couples the communication states of theextracted app communication paths. The logical coupling means thatinformation items of the reception states of the diagnosticcommunication packets of the devices are represented as one table forthe transmission devices which are common items in order to compare thecommunication states of the app communication paths of the devices, andthe details will be described with reference to FIGS. 11A and 11B. Asfor the logically coupled communication states of the app communicationpaths, it is easy to compare the state of the app communication path ina case where the terminal device 13 and the terminal device 14 which arethe utilization devices use the app 113 provided by the processingdevice 11 a and the state of the app communication path in a case wherethe terminal device 13 and the terminal device 14 use the app 123provided by the processing device 12. For example, the comparison of thestates of the communication paths may be performed by performing thecomparison using the number of app communication paths capable ofcommunicating in a case where the apps are used. The app of which thenumber of app communication paths capable of communicating is large hasa high degree of availability to the utilization device. Informationitems of the communication states of the app communication paths coupledwith the live list comparison function of the live list comparator anddeterminer 119 are generated from information items of the receptionstates of the diagnostic communication packets output from the live listextractor 118, and the communication states thereof are compared.

The live list determination function of the live list comparator anddeterminer 119 determines the processing state set to be in the activestate and the processing device set to be in the standby state among theprocessing devices constituting the redundant pair. Specifically, thelive list comparator and determiner 119 determines whether any one ofthe processing device 11 a and the processing device 12 constituting theredundant pair is set to be in the active state or the standby statebased on the coupled information items of the communication pathsacquired from the live list extractor 118. For example, the live listdetermination function compares the number (normal number) of appcommunication paths of in the processing device 11 a and the processingdevice 12 which are capable of normally communicating with the terminaldevice 13 and the terminal device 14 which are the communicationpartners of the app 113 and the app 123, and determines to set thedevice having a larger normal number to be in the active state and theother device to be in the standby state. The live list comparator anddeterminer 119 outputs the determination result to the switch 110.

The switch 110 maintains the operation state of the processing device 11a or switches the processing device 11 a to the stoppage state based onthe determination of the live list comparator and determiner 119 whetherthe app 113 continues the operation. The processing device 11 a which isthe second configuration example of the processing device is differentfrom the processing device 11 in that the processing device 11 a can bespontaneously stopped except that the processing device 11 is stoppeddue to the failure but other than that the processing device 11 iscontinuously operated in principle. The processing device 11 a isspontaneously stopped, and thus, it is possible to improve theavailability of the utilization device. When the switching of apps isrequired, as described in the step 16, the transmission of thediagnostic communication packets may be stopped after stopping the app113 instead of stopping the processing device 11 a.

Although it has been described in the present embodiment that the livelist comparator and determiner 119 is spontaneously stopped with thesimple comparison of the normal number of app communication paths as adetermination criterion, the determination criterion is not limited tothis example. For example, the live list comparator and determiner 119may use a communication speed in the communication between the app andthe utilization device, a network distance between the app and theutilization device, an operation time of the processing device, energyefficiency, failure result, or another cause, as the determinationcriterion.

Hereinabove, a description of the second configuration example of theprocessing device using FIG. 9 has been described.

Hereinafter, the app communication path will be described with referenceto FIG. 10. FIG. 10 is a diagram showing an example of the appcommunication path of the processing system according to the embodiment.

In FIG. 10, the processing device 11, the processing device 12, theterminal device 13, and the terminal device 14 transmit and receive thediagnostic communication packets in the communication paths,respectively. For example, a communication path A is used in the packettransmission between the processing device 11 and the terminal device13. Similarly, it is assumed that the communication path between theprocessing device 11 and the terminal device 14 is referred to as B, thecommunication path between the processing device 12 and the terminaldevice 13 is referred to as C, the communication path between theprocessing device 12 and the terminal device 14 is referred to as D, thecommunication path between the terminal device 13 and the terminaldevice 14 is referred to as E, and the communication path between theprocessing device 11 and the processing device 12 is referred to as F.Numerals 1 and 2 are assigned to the transmission directions of thecommunication paths A to F. For example, A1 indicates a direction fromthe processing device 11 to the terminal device 13, and A2 is a reverseddirection thereof.

The app communication paths are communication paths used by the terminaldevice 13 and the terminal device 14, and are the communication paths Ato E among the communication paths A to F shown in FIG. 10. The livelist extractor 118 extracts the live lists in both directions of the appcommunication path. That is, the live list extractor 118 counts thenormal number of communication paths A to E in both directions.Meanwhile, since the communication path F is not used in the appcommunication of the terminal device 13 and the terminal device 14, thelive list extractor 118 does not extract the state of the communicationpath.

Hereinabove, a description of the app communication path using FIG. 10has been described.

Hereinafter, the logical coupling of the live lists will be describedwith reference to FIGS. 11A and 11B. FIGS. 11A and 11B are diagramsshowing examples of the logical coupling of the live lists according tothe embodiment.

FIG. 11A shows the logical coupling of the live lists in a case wherethe communication path A1 of FIG. 10 fails. FIGS. 11A and 11B show thelive list (LL11) of the processing device 11, the live list (LL12) ofthe processing device 12, the live list (LL13) of the terminal device13, and the live list (LL14) of the terminal device 14 transmittedthrough the broadcast. In FIG. 11A, since the live list (LL13) of theterminal device 13 shows that the diagnostic communication packet fromthe processing device 11 fails, the item of “whether or not diagnosticcommunication is received” is “x” in “PC11” of the item of “diagnosticcommunication transmitter”. The indication “-” means a path which is notestablished as the app communication path.

A table acquired by logically coupling the live lists LL11 to LL14 is alogical coupling table TB11 on a right side of an arrow. The logicalcoupling table TB11 summarizes the item of “diagnostic communicationtransmitter” of the live list as a “transmitter side” and a generator ofthe live lists as “receiver side”. In the logical coupling table TB11,the state corresponding to the “PC11” on the “transmitter side” and the“PC13” on the “receiver side” is “x”.

Here, the normal number of communication paths between the terminaldevice 13 and the processing device 11 (PC11) (both directions) is 3.Meanwhile, the normal number of communication paths between the terminaldevice 13 and the processing device 12 (PC12) (both directions) is 4.Accordingly, since the normal number of communication paths in a casewhere the processing device 12 provides the service using the app 123 isgreater than that in a case where the processing device 11 provides theservice using the app 113, the live list comparator and determiner 119of FIG. 9 sets the app 113 to be in the stoppage state. The app 113 isset to be in the stoppage state, and thus, the app 123 becomes activedue to the redundant operation.

FIG. 11B shows the logical coupling of the live lists in a case wherethe communication path A2 of FIG. 10 fails. In FIG. 11B, since the livelist (LL11) of the processing device 11 shows that the diagnosticcommunication packet from the terminal device 13 fails, the item of“whether or not diagnostic communication is received” is “x” in the“PC13” of the item of the “diagnostic communication transmitter”. Sincethe live list (LL13) of the terminal device 13 cannot be transmitted tothe processing device 11, the content of the live list (LL13) is notapparent.

Here, a table acquired by logically coupling the live lists LL11 to L114is a logical coupling table TB11. In the logical coupling table TB11,the state corresponding to the “PC13” on the “transmitter side” and the“PC11” on the “receiver side” is “x”.

Here, the normal number of communication paths between the terminaldevice 13 and the processing device 11 (PC11) (both directions) is 2.Meanwhile, the normal number of communication paths between the terminaldevice 13 and the processing device 12 (PC12) (both directions) is 3.Accordingly, since the normal number of communication paths in a casewhere the processing device 12 provides the service using the app 123 isgreater than that in a case where the processing device 11 provides theservice using the app 113, the live list comparator and determiner 119of FIG. 9 sets the processing device 11 to be in the stoppage state. Theprocessing device 11 is set to be in the stoppage state, and thus, anydevices do not receive the diagnostic communication packets from theprocessing device 11. Therefore, the state of the processing device 12is switched from the standby state to the active state, and the app 123is operated.

Since FIGS. 11A and 11B show the case where the communication path Arelated to the processing device 11 fails, even in a case where thelogical coupling table TB11 is not used, it is easy to determine whetheror not to set the processing device 11 to be in the stoppage state.However, for example, it is not easy to determine the redundantoperation in a case where a part of both the communication path relatedto the processing device 11 and the communication path related to theprocessing device 12 fails. A predetermined condition is applied usingthe logical coupling table TB11, and thus, it is possible to easilyautomate the determination of the redundant operation.

Hereinabove, a description of the logical coupling of the live listsusing FIGS. 11A and 11B has been described.

Hereinafter, a switching operation of the processing device 11 a will bedescribed with reference to FIG. 12. FIG. 12 is a flowchart showing anexample of the switching operation of the processing device according tothe embodiment.

In FIG. 12, it is determined whether or not the processing device 11 ais in the active state (step S41). For example, whether or not theprocessing device is in the active state may be determined by the stateof the app 113 retained in the switch 110. In a case where it isdetermined that the processing device is not in the active state (in acase where the processing device is in the standby state) (step S41:NO), the processing device 11 a ends the process of the switchingoperation shown in the flowchart of FIG. 12.

Meanwhile, in a case where it is determined that the processing deviceis in the active state (step S41: YES), the processing device 11 alogically couples the acquired live lists (step S42). The live listscoupled in step S42 are the live lists (LL11 to LL14) as described inFIGS. 11A and 11B.

After the process of step S42 is performed, the processing device 11 aanalyzes the app communication paths (step S43). The analysis of the appcommunication paths is the comparison of the normal number of appcommunication paths described in FIGS. 11A and 11B. Here, the analysismethod of the app communication paths is not limited to the comparisonof the normal number of app communication paths. For example, thecommunication speed of the app communication path, the network distancebetween the app and the utilization device, the operation time of theprocessing device, the energy efficiency, the failure result, or anothercause may be used as the determination criterion.

After the process of step S43 is performed, the processing device 11 adetermines whether or not the case where the process is provided by theprocessing device 12 instead of the processing device 11 a is moreadvantageous than that in the case where the process is provided by theprocessing device 11 a, based on the analysis result (step S44). Thedetermination in the process of step S43 is based on the content of theanalysis in the process of step S43 such as comparison of the normalnumber of app communication paths.

In a case where it is determined that the case where the process isprovided by the processing device 12 is more advantageous than that inthe case where the processing is provided by the processing device 11 a(step S44: YES), the state of the processing device 11 a is switchedfrom the active state to the standby state (step S45). In the method ofswitching the state of the processing device 11 a from the active stateto the standby state, the switch 110 described in FIG. 9 stops theprocessing device 11, and thus, the processing device 12 can be in theactive state.

Meanwhile, in a case where it is determined that the case where theprocess is provided by the processing device 12 is not more advantageousthan that in the case where the process is provided by the processingdevice 11 a (step S44: NO), the processing device 11 a ends the processof the switching operation shown in the flowchart of FIG. 12. That is,the operation state of the processing device 11 is maintained.

For example, the transition of the processing device 11 a that entersthe standby state once to the active state again is performed in therestarting (reset process) of the device.

Hereinabove, a description of the switching operation of the processingdevice 11 a using FIG. 12 has been described.

Although in the above-described processing system the operations of theprocessing device and the terminal devices are described based on thefunctions thereof, these functions may be operated in the same device.These functions may be distributed and performed in the same processingsystem.

As described above, a processing device according to an embodimentincludes a provider that provides a process to a utilization deviceconnected to a network of a process control system in a plant, aacquirer that acquires live lists generated in other devices connectedto the network based on diagnostic communication packets transmittedfrom another processing device that provides a process to theutilization device at predetermined time intervals, and a switch thatswitches a state of the provider from a standby state in which theprovider is on standby to provide the process to the utilization deviceto an active state in which the provider provides the process based onthe acquired live lists. Accordingly, it is possible to realize ahigh-stability redundant configuration with low cost.

A control method of a processing device of an embodiment includes aprocess provision step of providing a process to a utilization deviceconnected to a network of a process control system in a plant, a livelist acquisition step of acquiring live lists generated in other devicesconnected to the network based on diagnostic communication packetstransmitted from another processing device that provides a process tothe utilization device at predetermined time intervals, and a switchingstep of switching a provision state of the process from a standby statein which the processing device is on standby to provide the process tothe utilization device to an active state in which the processing deviceprovides the process based on the acquired live lists. Accordingly, itis possible to realize a high-stability redundant configuration with lowcost.

The steps in the process according to the present embodiment are notlimited to the above-described order and may be performed in anarbitrary order.

The present embodiment may be performed in the following aspects.

For example, the present embodiment may use a network communicationfunction of the process control system. The present embodiment may beused in a system in which control processing devices or a controlprocessing device and an operation-monitoring device are connected viathe network in the process control system.

The present embodiment may be adopted in a system in which the appcommunication address and the diagnostic communication address areautomatically allocated and managed. For example, the present embodimentmay be adopted in a system such as a FOUNDATION Fieldbus protocol (Highspeed Ethernet (HSE)) or a Vnet/IP (registered trademark) protocol. Inthe case of the Vnet/IP protocol, a Vnet address is used as the appcommunication address, and an IP address is used as the diagnosticcommunication address.

A program for realizing the functions of the devices described in thepresent embodiment may be recorded in a computer-readable recordingmedium, and various processes of the present embodiment may be performedby reading the program recorded in the recording medium into a computersystem and executing the read program. The “computer system” mentionedherein may include an OS or hardware such as a peripheral device. It isassumed that the “computer system” includes a homepage provisionenvironment (or a display environment) as long as a WWW system is used.The “computer-readable recording medium” refers to a writablenonvolatile memory such as a flexible disk, a magneto-optical disk, aROM, or a flash memory, a portable medium such as a CD-ROM, or a storagedevice such as a hard disk built in the computer system.

It is assumed that the “computer-readable recording medium” includes amedium that retains the program for a predetermined time, such as avolatile memory (for example, a dynamic random-access memory (DRAM)within a computer system which is a server or a client in a case wherethe program is transmitted via a communication line such as a telephoneline or a network such as the Internet. The program may be transmittedto another computer system using a transmission medium or a transmissionwave of the transmission medium from the computer system that stores theprogram in the storage device. Here, the “transmission medium” thattransmits the program refers to a medium having a function oftransmitting information such as a communication line such as atelephone line or a network such as the Internet. The program may beused for realizing a part of the above-described functions. The programmay be a so-called difference file (difference program) realized bycombining the above-described functions with the program alreadyrecorded in the computer system.

While the embodiment of the present invention has been described withreference to the drawings, the specific configuration is not limited tothe embodiment, and the embodiment includes various changes withoutdeparting from the gist of the present invention.

What is claimed is:
 1. A processing device, comprising: at least onememory storing instructions, and at least one processor configured toexecute the instructions to: provide a process to a first deviceconnected to a network of a process control system in a plant; acquire alive list generated by the first device based on diagnosticcommunication packets transmitted from the first device at predeterminedtime intervals, the live list comprising information indicating whethercommunication between the first device and another processing devicethat provides a process to the first device is normal, the processingdevice and the another processing device constituting a redundant pair;and switch a provision state of the process from a standby state inwhich the processing device is on standby to provide the process to thefirst device to an active state in which the processing device providesthe process to the first device based on the acquired live list, whereinthe at least one processor is configured to execute the instructions to:acquire a plurality of live lists from a plurality of devices connectedto the network; and switch the provision state of the process from thestandby state to the active state when all the plurality of live listsacquired within a predetermined period include the informationindicating that the communication between the first device and theanother processing device is not normally operated, wherein the at leastone processor is configured to execute the instructions to: provide aprocess to a second device connected to the network; receive: a firstdiagnostic communication packet generated by and transmitted from thefirst device, the first diagnostic communication packet including afirst live list including information indicating whether communicationbetween the first device and the another processing device is normallyoperated, information indicating whether communication between the firstdevice and the processing device is normally operated, and informationindicating whether communication between the first device and the seconddevice is normally operated; and a second diagnostic communicationpacket generated by and transmitted from the second device, the seconddiagnostic communication packet including a second live list includinginformation indicating whether communication between the second deviceand the another processing device is normally operated, informationindicating whether communication between the second device and theprocessing device is normally operated, and information indicatingwhether communication between the second device and the first device isnormally operated; acquire the first live list from the first diagnosticcommunication packet and the second live list from the second diagnosticcommunication packet; and switch the provision state of the process fromthe standby state to the active state when both of the first and secondlive lists acquired within a predetermined period include informationindicating that the communication with the another processing device isnot normally operated.
 2. The processing device according to claim 1,wherein the at least one processor is configured to execute theinstructions to: receive the diagnostic communication packets; generatethe live list based on the received diagnostic communication packets;and transmit the generated live list as a part of diagnosticcommunication packets of the processing device at predetermined timeintervals.
 3. The processing device according to claim 2, wherein the atleast one processor is configured to execute the instructions to:transmit the diagnostic communication packets to all communicationdestinations that communicate when the process of the processing deviceis used in the first device.
 4. The processing device according to claim2, wherein the at least one processor is configured to execute theinstructions to: generate the live list based on the diagnosticcommunication packets of all communication destinations that communicatewhen the other processing device is used.
 5. A processing device,comprising: at least one memory storing instructions, and at least oneprocessor configured to execute the instructions to: provide a processto a first device connected to a network of a process control system ina plant; transmit diagnostic communication packets at predetermined timeintervals; acquire a live list based on diagnostic communication packetsgenerated by the first device and transmitted from the first device atpredetermined time intervals, the live list comprising information onoperation state of devices of transmission sources of the diagnosticcommunication packets; and switch a provision state of the process to astandby state in which the processing device is on standby to providethe process to the first device based on the acquired live list, whereinthe at least one processor is configured to execute the instructions to:acquire a plurality of live lists from a plurality of devices connectedto the network; analyze a communication state of a communication pathbetween the processing device and the first device using the live listsacquired within a predetermined period; and switch the provision stateof the process to the standby state and stop the transmitting of thediagnostic communication packets when a communication state between thefirst device and another processing device that provides a process tothe first device has a priority higher than a communication statebetween the first device and the processing device, the processingdevice and the another processing device constituting a redundant pair,wherein the at least one processor is configured to execute theinstructions to: provide a process to a second device connected to thenetwork; receive: a first diagnostic communication packet generated byand transmitted from the first device, the first diagnosticcommunication packet including a first live list including informationindicating whether communication between the first device and theanother processing device is normally operated, information indicatingwhether communication between the first device and the processing deviceis normally operated, and information indicating whether communicationbetween the first device and the second device is normally operated; anda second diagnostic communication packet generated by and transmittedfrom the second device, the second diagnostic communication packetincluding a second live list including information indicating whethercommunication between the second device and the another processingdevice is normally operated, information indicating whethercommunication between the second device and the processing device isnormally operated, and information indicating whether communicationbetween the second device and the first device is normally operated;acquire the first live list from the first diagnostic communicationpacket and the second live list from the second diagnostic communicationpacket; analyze the communication state of the communication pathbetween the processing device and the first device using the first andsecond live lists acquired within the predetermined period; and switchthe provision state of the process to the standby state when thecommunication state between the first device and the another processingdevice has a priority higher than the communication state between thefirst device and the processing device.
 6. The processing deviceaccording to claim 5, wherein the at least one processor is configuredto execute the instructions to: transmit the diagnostic communicationpackets to all communication destinations that communicate when theprocess of the processing device is used in the first device.
 7. Theprocessing device according to claim 5, wherein the at least oneprocessor is configured to execute the instructions to: receivediagnostic communication packets transmitted from the another processingdevice; and generate a live list based on the received diagnosticcommunication packets, transmit the generated live list as a part of thediagnostic communication packets of the processing device atpredetermined time intervals.
 8. A network device connected to a networkof a process control system in a plant and configured to transmitdiagnostic communication packets to a processing device according toclaim 1, the network device comprising: at least one memory storinginstructions, and at least one processor configured to execute theinstructions to: receive diagnostic communication packets transmittedfrom the processing device at predetermined time intervals; generate alive list based on the received diagnostic communication packets, thelive list comprising information on operation state of devices oftransmission sources of the diagnostic communication packets; andtransmit the generated live list as a part of diagnostic communicationpackets of the network device at predetermined time intervals.
 9. Acontrol method of a processing device, comprising: providing a processto a first device connected to a network of a process control system ina plant; acquiring a live list generated by the first device based ondiagnostic communication packets transmitted from the first device atpredetermined time intervals, the live list comprising informationindicating whether communication between the first device and anotherprocessing device that provides a process to the first device is normal,the processing device and the another processing device constituting aredundant pair; and switching a provision state of the process from astandby state in which the processing device is on standby to providethe process to the first device to an active state in which theprocessing device provides the process to the first device based on theacquired live list, wherein the control method comprises: acquiring aplurality of live lists from a plurality of devices connected to thenetwork; and switching the provision state of the process from thestandby state to the active state when all the plurality of live listsacquired within a predetermined period include the informationindicating that the communication between the first device and theanother processing device is not normally operated, wherein the controlmethod comprises: providing a process to a second device connected tothe network; receiving: a first diagnostic communication packetgenerated by and transmitted from the first device, the first diagnosticcommunication packet including a first live list including informationindicating whether communication between the first device and theanother processing device is normally operated, information indicatingwhether communication between the first device and the processing deviceis normally operated, and information indicating whether communicationbetween the first device and the second device is normally operated; anda second diagnostic communication packet generated by and transmittedfrom the second device, the second diagnostic communication packetincluding a second live list including information indicating whethercommunication between the second device and the another processingdevice is normally operated, information indicating whethercommunication between the second device and the processing device isnormally operated, and information indicating whether communicationbetween the second device and the first device is normally operated;acquiring the first live list from the first diagnostic communicationpacket and the second live list from the second diagnostic communicationpacket; and switching the provision state of the process from thestandby state to the active state when both of the first and second livelists acquired within a predetermined period include informationindicating that the communication with the another processing device isnot normally operated.
 10. A control method of a processing device,comprising: providing a process to a first device connected to a networkof a process control system in a plant; transmitting diagnosticcommunication packets at predetermined time intervals; acquiring a livelist based on diagnostic communication packets generated by the firstdevice and transmitted from the first device at predetermined timeintervals, the live list comprising information on operation state ofdevices of transmission sources of the diagnostic communication packets,and switching a provision state of the process to a standby state inwhich the processing device is on standby to provide the process to thefirst device based on the acquired live list, wherein the control methodcomprises: acquiring a plurality of live lists from a plurality ofdevices connected to the network; analyzing a communication state of acommunication path between the processing device and the first deviceusing the live lists acquired within a predetermined period; andswitching the provision state of the process to the standby state andstopping the transmitting of the diagnostic communication packets when acommunication state between the first device and another processingdevice that provides a process to the first device has a priority higherthan a communication state between the first device and the processingdevice, the processing device and the another processing deviceconstituting a redundant pair, wherein the control method comprises:providing a process to a second device connected to the network;receiving: a first diagnostic communication packet generated by andtransmitted from the first device, the first diagnostic communicationpacket including a first live list including information indicatingwhether communication between the first device and the anotherprocessing device is normally operated, information indicating whethercommunication between the first device and the processing device isnormally operated, and information indicating whether communicationbetween the first device and the second device is normally operated; anda second diagnostic communication packet generated by and transmittedfrom the second device, the second diagnostic communication packetincluding a second live list including information indicating whethercommunication between the second device and the another processingdevice is normally operated, information indicating whethercommunication between the second device and the processing device isnormally operated, and information indicating whether communicationbetween the second device and the first device is normally operated;acquiring the first live list from the first diagnostic communicationpacket and the second live list from the second diagnostic communicationpacket; analyzing the communication state of the communication pathbetween the processing device and the first device using the first andsecond live lists acquired within the predetermined period; andswitching the provision state of the process to the standby state whenthe communication state between the first device and the anotherprocessing device has a priority higher than the communication statebetween the first device and the processing device.
 11. A control methodof a network device connected to a network of a process control systemin a plant and configured to transmit diagnostic communication packetsto a processing device according to claim 1, comprising: receivingdiagnostic communication packets transmitted from the processing deviceat predetermined time intervals; generating a live list based on thereceived diagnostic communication packets, the live list comprisinginformation on operation state of devices of transmission sources of thediagnostic communication packets; and transmitting the generated livelist as a part of diagnostic communication packets of the network deviceat predetermined time intervals.
 12. A non-transitory computer-readablestorage medium storing a control program of a processing device, whichwhen executed by a computer, causes the computer to execute: providing aprocess to a first device connected to a network of a process controlsystem in a plant; acquiring a live list generated by the first devicebased on diagnostic communication packets transmitted from the firstdevice at predetermined time intervals, the live list comprisinginformation indicating whether communication between the first deviceand another processing device that provides a process to the firstdevice is normal, the processing device and the another processingdevice constituting a redundant pair; and switching a provision state ofthe process from a standby state in which the processing device is onstandby to provide the process to the first device to an active state inwhich the processing device provides the process to the first devicebased on the acquired live list, wherein the control program of theprocessing device, which when executed by the computer, causes thecomputer to execute: acquiring a plurality of live lists from aplurality of devices connected to the network; and switching theprovision state of the process from the standby state to the activestate when all the plurality of live lists acquired within apredetermined period include the information indicating that thecommunication between the first device and the another processing deviceis not normally operated, wherein the control program of the processingdevice, which when executed by the computer, causes the computer toexecute: providing a process to a second device connected to thenetwork; receiving: a first diagnostic communication packet generated byand transmitted from the first device, the first diagnosticcommunication packet including a first live list including informationindicating whether communication between the first device and theanother processing device is normally operated, information indicatingwhether communication between the first device and the processing deviceis normally operated, and information indicating whether communicationbetween the first device and the second device is normally operated; anda second diagnostic communication packet generated by and transmittedfrom the second device, the second diagnostic communication packetincluding a second live list including information indicating whethercommunication between the second device and the another processingdevice is normally operated, information indicating whethercommunication between the second device and the processing device isnormally operated, and information indicating whether communicationbetween the second device and the first device is normally operated;acquiring the first live list from the first diagnostic communicationpacket and the second live list from the second diagnostic communicationpacket; and switching the provision state of the process from thestandby state to the active state when both of the first and second livelists acquired within a predetermined period include informationindicating that the communication with the another processing device isnot normally operated.
 13. A non-transitory computer-readable storagemedium storing a control program of a processing device, which whenexecuted by a computer, causes the computer to execute: providing aprocess to a first device connected to a network of a process controlsystem in a plant; transmitting diagnostic communication packets atpredetermined time intervals; acquiring a live list based on diagnosticcommunication packets generated by the first device and transmitted fromthe first device at predetermined time intervals, the live listcomprising information on operation state of devices of transmissionsources of the diagnostic communication packets; and switching aprovision state of the process to a standby state in which theprocessing device is on standby to provide the process to the firstdevice based on the acquired live list, wherein the control program ofthe processing device, which when executed by the computer, causes thecomputer to execute: acquiring a plurality of live lists from aplurality of devices connected to the network; analyzing a communicationstate of a communication path between the processing device and thefirst device using the live lists acquired within a predeterminedperiod; and switching the provision state of the process to the standbystate and stopping the transmitting of the diagnostic communicationpackets when a communication state between the first device and anotherprocessing device that provides a process to the first device has apriority higher than a communication state between the first device andthe processing device, the processing device and the another processingdevice constituting a redundant pair, wherein the control program of theprocessing device, which when executed by a computer, causes thecomputer to execute: providing a process to a second device connected tothe network; receiving: a first diagnostic communication packetgenerated by and transmitted from the first device, the first diagnosticcommunication packet including a first live list including informationindicating whether communication between the first device and theanother processing device is normally operated, information indicatingwhether communication between the first device and the processing deviceis normally operated, and information indicating whether communicationbetween the first device and the second device is normally operated; anda second diagnostic communication packet generated by and transmittedfrom the second device, the second diagnostic communication packetincluding a second live list including information indicating whethercommunication between the second device and the another processingdevice is normally operated, information indicating whethercommunication between the second device and the processing device isnormally operated, and information indicating whether communicationbetween the second device and the first device is normally operated;acquiring the first live list from the first diagnostic communicationpacket and the second live list from the second diagnostic communicationpacket; analyzing the communication state of the communication pathbetween the processing device and the first device using the first andsecond live lists acquired within the predetermined period; andswitching the provision state of the process to the standby state whenthe communication state between the first device and the anotherprocessing device has a priority higher than the communication statebetween the first device and the processing device.
 14. A non-transitorycomputer-readable storage medium storing a control program of a networkdevice which is connected to a network of a process control system in aplant and configured to transmit diagnostic communication packets to aprocessing device according to claim 1, which when executed by acomputer, causes the computer to execute: receiving diagnosticcommunication packets transmitted from the processing device atpredetermined time intervals; generating a live list based on thereceived diagnostic communication packets, the live list comprisinginformation on operation state of devices of transmission sources of thediagnostic communication packets; and transmitting the generated livelist as a part of diagnostic communication packets of the network deviceat predetermined time intervals.